The present invention relates generally to dispensing systems for chemical reactants, and in particular, to the combination of a self-contained, self-regulating pressure generating system and an apparatus for mixing and dispensing the individual reactive components. More particularly, in a preferred embodiment, the invention relates to a system for dispensing two separately contained, reactive liquids and causing them to flow into a mixing nozzle wherein a cross linking reaction will take place, wherein a blowing agent will cause the resins comprising the material to begin forming a chemical foam.
In a further aspect, the present invention utilizes the same gas that is used to dispense one or more liquids under pressure to entrain the foam being formed and propel it to the point of application.
In a specific embodiment, the invention relates to a system for generating carbon dioxide which serves the multiple purposes of causing a liquid hydroxyl-rich resin from one flexible walled container and an isocyanate material from a second flexible walled container, to flow to a dispensing gun having a removable mixing and dispensing nozzle. At the same time, part of the generated gas is directed through the same gun, impinging on and serving to propel the materials being mixed to the point of application. In this connection, mixture of the isocyanate or "A" component and the resin or "B" component is normally a thermosetting reaction which can also be made to generate a gas for the purpose of "blowing" the constituents into a foam. Such a foam, when being mixed with a swirling action inside a mixing and dispensing nozzle, can be directed to the outlet of a tube from which the same gas used to urge the components into the mixing chamber is discharged at atmospheric pressure. As the mix just beginning to foam impinges upon the gas stream, the being-formed foam will be picked up and propelled to a surface to which it is being applied.
In the past, successful systems for dispensing urethane foam have been produced. These include those described in U.S. Pat. No. 3,784,110 and U.S. Pat. No. 4,676,437, for example. In these systems, when the individual constituents are mixed, the heat of reaction and the lowering of pressure incident to discharge caused foaming of an emulsified gas or vapor, usually a fluorocarbon such as a "Freon." The over pressure from the dissolved gas was sufficient to propel the mixed chemicals and the being-foamed to the point of application. Many thousands of portable kits using this principle were sold, and such products were considered highly successful.
However, recent concern with the impact of fluorocarbon blowing agents and propellants on the earth's atmosphere have made it desirable to terminate the use of these propellants. It is widely believed that such propellants, when released into the atmosphere, eventually find their way to high altitudes and are incidental in the destruction of the earth's protective ozone layer.
Consequently, while the use of such propellants is now being ruled out, there are no readily available substitutes for certain of these liquid fluorocarbons that do not have other serious drawbacks. Thus, an advantage of fluorocarbon propellants was that they were able to change from liquid to vapor form at modest pressures and temperatures. Hence, they could be liquified without dangerously high pressures and yet could provide excellent expansion and propulsion potential.
While foam dispensed and blown using the fluorocarbons or chloro-fluorocarbons have had significant advantages, most or all packaged systems using such foams did suffer from the drawback of lacking regulated pressure. Thus, the dispensing rate tended to become lower with the passage of time as the effective headspace pressure in the area containing the liquids was reduced as the gasses were exhausted. A system with a self-regulating pressure arrangement would thus be advantageous for maintaining a relatively constant dispensing rate which would also be advantageous for mixing.
Other potential, readily liquefiable vapors, however, have their own drawbacks, and as a consequence, it has not been practical to use them in foam dispensing and other related applications. The propellants of the kind in question include butane and propane, for example, which are highly flammable, and which require special protection against fire and/or explosion hazards, particularly during shipment and storage.
As a result of the foregoing situation, there has been a need to mix and dispense foam-forming and other chemicals in a way that is as economical and practical as prior art practice, but without their associated drawbacks. One very advantageous propellant, for example, is carbon dioxide. Such a gas can be made to serve both the blowing or expansion requirements of foam-forming and the role of propellant.
However, because of the nature of carbon dioxide, it requires extremely high pressures to be liquified. As a consequence, while it is possible to use liquid or highly compressed carbon dioxide confined under great pressures for some dispensing application, such as for dispensing carbonated beverages, for example, this requires using high pressure containers and accurate pressure regulation systems. Thus, while CO.sub.2 is an excellent propellant, pressure tanks and regulators are too expensive enough to be discarded after use. Compressed gases are also the subject of prohibitive freight rates and storage requirements. In this connection, materials which are "hazardous," either by risk of flammability or high pressure, or both, require special precautions for shipping, including special packaging, and special labeling. These products involve concomitantly high freight rates and storage practices which are inconsistent with economical throwaway packaging.
While it has been suggested that certain mixing and propellant compositions could be made at the site wherein they are to be utilized in a dispensing operation, it is also inconsistent with the purpose of providing a convenient portable dispensing apparatus to require wet chemical mixing by the foam applicators or other operators. One of the reasons for the success of low-cost packaged kits able to mix and dispense foam-making chemicals is their foolproof nature and their lack of a requirement for precise measuring on or near the job site. Another problem with generating gases, especially CO.sub.2, is that gas pressure must be regulated to be practical. Foam applications usually require up to 100 psi or even much more, preferably in the 40-80 or 50-70 psi ranges.
In view of the failure of the prior art to provide a self-contained mixing and dispensing system for reactive chemicals, particularly those used to create expanded cellular plastics such as urethane foams, it is an object of the invention to provide an improved gas-generating and dispensing apparatus.
Another object of the invention is to provide a container system which includes a chemical reagents which are isolated from each other for shipment but which may thereafter be activated so as to begin generating gas for the purpose of mixing and dispensing chemical foams.
A further object of the invention is to provide a simplified, low cost system for generating propellant gases, including carbon dioxide, in which the reagents used to create the propellant gas are held separate from each other until it is desired to initiate the mixing reaction.
A still further object of the invention is to provide a gas-generating system which is inherently able to regulate the pressure of gas being generated over a significant period of time.
Yet another object of the invention is to provide a gas-generating arrangement which provides essentially self-regulated pressure in a selected range.
Another object of the invention is to provide an inherently self-regulating pressure control arrangement wherein gas pressure results from mixing two or more reactants, and wherein the system includes separate containers for each of the reactants and an arrangement of containers, passages, and fittings or the like whereby a decrease in pressure caused by using the gas causes additional gas forming chemicals to be supplied for mixing with each other so as to again increase the system pressure to a controlled level.
A further object of the invention is to provide a packaged dispensing system which includes a dispensing gun having a removable mixing and dispensing nozzle including at least two liquid inlet passages and a separate gas passage for dispensing the foam product, with the system further including sealed containers with gas-generating components and an arrangement of passage tubes and seals permitting the reactants to be mixed when desired by the user.
A still further object of the invention is to provide a combination dispensing gun and gas-generating apparatus wherein the entire package contains relatively non-toxic, non-corrosive chemicals able to be shipped at minimum expense while unpressurized, and yet being activatable upon demand to supply a regulated dispensing pressure.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a combination gas-generating and liquid dispensing system with a self-regulating pressure arrangement. The invention also achieves its objects by providing a gas-generating and dispensing system that includes a master container that in turn includes one or more containers of dispensible fluent materials and is able to be pressurized by a generated gas, a generator having at least two containers with gas producing reactants separately contained therein, an arrangement of passages between the containers whereby controlled mixing of the gas-generating materials can be achieved in practice, and a dispensing gun with valves for controlling liquid and gas flow therethrough.
The manner in which the foregoing and other objects and advantages of the invention achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings wherein like reference numbers indicate corresponding parts throughout.